THURSDAY, Aug. 29 (HealthDay News) -- About 4 percent of American adults -- more than 8.5 million people -- have used a prescription sleep aid in the past month, and the use increases with age, U.S. health officials reported Thursday.

In addition, more women (5 percent) than men (3.1 percent) over the age of 20 take these drugs, and those with higher education levels are more likely to use them, the researchers from the U.S. Centers for Disease Control and Prevention found.

"This is the first time we have a national estimate on how many people are taking prescription medications for sleep," said report coauthor Yinong Chong, an epidemiologist at the CDC's National Center for Health Statistics.

In the past 20 years, there has been reports of an increased number of prescriptions for sleep aids in the United States. But, Chong said, the use of such drugs has remained stable in the past decade, rising about only 1 percent between 1999 to 2010.

Using data from the National Health and Nutrition Examination Survey, 2005 to 2010, the CDC researchers found that self-reported use of the sleep aids was lowest among the youngest age group (those between 20 and 39 years old) at about 2 percent, but it increased to 6 percent among those aged 50 to 59 and reached 7 percent among those 80 and older.

Dr. Jordan Josephson, a nasal and endoscopic sinus surgeon at Lenox Hill Hospital in New York City, said he was not surprised by the numbers because "sleep disorders have been estimated to affect 50 million to 70 million Americans."

"More accurate diagnosis and better education has led more people to seek treatment for these disorders, which affect them in every aspect of their lives," Josephson said.

For example, snoring and sleep apnea are the No. 1 medical cause of relationship breakups and divorce, Josephson said. Insomnia leads to fatigue, which leads to poor performance at work and school, as well as motor vehicle accidents and injuries while using heavy machinery, he added.

"For those people who suffer from fatigue and/or daytime somnolence -- being tired and feeling sleepy -- it is important for them to seek treatment from a board-certified sleep specialist," he said. "With proper diagnosis and treatment, these patients will have an improved quality of life."

Sleep-aid drugs have, however, become a new focus for the U.S. Food and Drug Administration over concerns that they may impact people's ability to drive the next morning. New evidence appears to confirm what many people have long suspected: that the effects of sleep drugs can persist well into the next day.

Last month, the FDA rejected an application for suvorexant, a new sleep drug from Merck, in part because tests showed that some people had difficulty driving the day after taking the drug.

The FDA said it was taking a closer look at all sleep medicines on the market and will ask manufacturers to conduct more extensive driving tests for all new sleep drugs.

For many people, insomnia may be tied to other chronic conditions that also need to be treated, another expert said.

Sleep medications are only part of the story, said Dr. Alon Avidan, director of the Sleep Disorders Center at the David Geffen School of Medicine at the University of California, Los Angeles. Many patients with insomnia also suffer from other problems, such as depression, chronic pain and mental disorders, he added.

"We should be looking at insomnia as not just managing the insomnia itself, but also treating the underlying disease," he said.

"But treating the underlying condition doesn't mean the insomnia will go away," he said. "What we generally do is we treat the insomnia separately from ... the underlying condition. When we treat both conditions, the end result is much better than addressing one symptom alone."

Other highlights of the report included:

Whites (4.7 percent) were more likely to use sleep aids than blacks (2.5 percent) or Mexican-Americans (2 percent).

People who used sleep aids the most were those who slept less than five hours (6 percent) and those who slept at least nine (5.3 percent). The researchers used the National Sleep Foundation's suggested guideline of seven hours of sleep as the minimum amount adults need for optimal performance.

One in six adults diagnosed with a sleep disorder and one in eight with trouble sleeping said they use sleep aids.